All solid-state Cr:LiSAF laser

Many kinds of experiments about all solid-state Cr:LiSAF lasers have been reported. A tunable all solid-state cw laser having tunability over more than 100 nm was developed by using the spectrum selection self-injection locking (SSSIL) method in 1992. The authors realize tunable picosecond radiation from an all solid-state laser with 146-200 ps pulses in an 88 nm range. Also, 70 fs pulse generation was achieved using a Kerr-lens mode-locking pumped with an Ar⁺ laser     

CO2 decomposition with oxygen-deficient Mn(II) ferrite

An oxygen-deficient Mn(II) ferrite (Mn_0.97Fe_2.02O_3.92) was synthesized and its reactivity to reduce CO₂ gas into carbon was studied at 300°C. The oxygen-deficient Mn(II) ferrite was obtained by flowing H₂ gas through Mn(II) ferrite with a nearly stoichiometric composition of Mn_0.97Fe_2.02O_4.00 at 300° C. The lattice constant of the oxygen-deficient Mn(II) ferrite (0.8505nm) is larger than that of the Mn(II) ferrite with a nearly stoichiometric composition (0.8498nm). The chemical composition of the Mn(II) ferrite changed from Mn_0.97Fe_2.02O_4.00 to Mn_0.97Fe_2.02O_3.92 during the H₂ reduction process, indicating that the oxygen is deficient in the spinel structure of the Mn(II) ferrite. This was confirmed by Mössbauer spectroscopy and X-ray diffractometry. The efficiency of CO₂ decomposition into carbon at 300°C with the oxygen-deficient Mn(II) ferrite was much lower by about 10⁵ than that of oxygen-deficient magnetite. This is considered to be due to the difference in electron conductivity between Mn(II) ferrite and magnetite, which determines the reductivity for CO₂ into carbon by donation of an electron at the adsorption site.     

Development of a hybrid catalytic combustor for a 1300°C class gas turbine

The hybrid catalytic combustor concept proposed by the authors has an advantage concerned with catalyst durability, because the catalyst is maintained below 1000°C even for application to 1300°C class gas turbines. A full-scale hybrid catalytic combustor has been designed for a 200 MW (1300°C) class gas turbine. The catalyst bed was 450 mm in diameter and consisted of a Pd/ alumina washcoat on a cordierite monolith. In experiments, the combustor has demonstrated the capability of meeting the NO_x emission level of SCR (selected catalytic reduction) during atmospheric pressure testing. To predict the catalyst performance at an elevated pressure, the characteristics of the catalyst were studied using a small scale reactor test, and a material property test using a DTA/TGA-Q.MASS system. The catalyst showed a higher activity in the oxidized state (PdO) than in the metallic state (Pd). This activity difference was governed by the equilibrium of the oxygen release from PdO in bulk. It was considered that oxidation rate of the metallic Pd in bulk was not so high and this caused self-oscillation for the Pd catalyst around the temperature of the oxygen release equilibrium. Even below the temperature of the oxygen release equilibrium, both surface and bulk (lattice) oxygen of the PdO was consumed by the methane oxidation reaction, and resulted in a lack of surface oxygen on the catalyst. This caused a reversible decrease in the catalyst activity during combustion testing, and indicated that the oxygen dissociation step was a rate limiting step in the catalytic combustion.     

Site-directed mutational analysis for the ATP binding of DnaA protein. Functions of two conserved amino acids (Lys-178 and Asp-235) located in the ATP-binding domain of DnaA protein in vitro and in vivo

DnaA protein, the initiator of chromosomal DNA replication in Escherichia coli, is activated by binding to ATP in vitro. We introduced site-directed mutations into two amino acids of the protein conserved among various ATP-binding proteins and examined functions of the mutated DnaA proteins, in vitro and in vivo. Both mutated DnaA proteins (Lys-178 --> Ile or Asp-235 --> Asn) lost the affinity for both ATP and ADP but did maintain binding activity for oriC. Specific activities in an oriC DNA replication system in vitro were less than one-tenth those of the wild-type protein. Assay of the generation of oriC sites sensitive to P1 nuclease, using the mutated DnaA proteins, revealed a defect in induction of the duplex opening at oriC. On the other hand, expression of each mutated DnaA protein in the temperature-sensitive dnaA46 mutant did not complement the temperature sensitivity. We suggest that Lys-178 and Asp-235 of DnaA protein are essential for the activity needed to initiate oriC DNA replication in vitro and in vivo and that ATP binding to DnaA protein is required for DNA replication-related functions.     

Studies on chitin. VI. Binding of metal cations

The adsorption abilities of chitin and its congeners with two series of degrees of deacetylation prepared by two different deacetylation procedures were compared. Among the polysaccharides obtained by the heterogeneous method, those with higher amino group content had higher adsorption ability. Plots of collection percentages versus amino group content, however, did not give straight lines. The plot for the chelation on the congeners that were prepared by homogeneous hydrolysis had a maximum at about 50% amino group content, and the value was higher than that for the sample with the highest amino group content, which was prepared by heterogeneous hydrolysis. These results suggest that the polysaccharides with about 50% amino group content obtained by the homogeneous procedure are potentially useful for the removal of metals.     

Thickness effect of notched metal sheets on deformation and fracture under tension

The deformation field in notched metal sheets stretched under tension was analysed experimentally. The results of strain distribution were explained by using the result of the near-tip deformation field of non-linear elastic material, combined with a simple model of the plastic state under a mixed plane stress and plane strain condition. Next, the relationship among fracture mechanics parameters, i.e. the notch-tip opening displacement, the notch-tip contraction and $\text{J-}\text{integral}$ was established based on the rigid plastic strip model. Finally, the effect of the specimen thickness on the toughness value at crack initiation and instability was discussed by improving Bluhm's idea that the total fracture resistance was the sum of the fracture work for slant and flat fractures.